cpprefjp.github.io/reference/map/map.html at master · cpprefjp/cpprefjp.github.io

946 lines (862 loc) · 62.4 KB
<!doctype html>
<html class="cpprefjp" lang="ja" itemscope="" itemtype="http://schema.org/WebPage">
<!-- Google tag (gtag.js) -->
<script async src="https://www.googletagmanager.com/gtag/js?id=G-NXNBNVBTJS"></script>
  window.dataLayer = window.dataLayer || [];
  function gtag(){dataLayer.push(arguments);}
  gtag('js', new Date());
  gtag('config', 'G-NXNBNVBTJS');
        <meta charset="UTF-8">
        <title>map - cpprefjp C++日本語リファレンス</title>
        <meta name="viewport" content="width=device-width,initial-scale=1">
        <meta name="keywords" content="
  C++,標準ライブラリ,リファレンス,ドキュメント,STL,std,map,std,class template
        <meta name="title" content="map - cpprefjp C++日本語リファレンス" />
        <meta itemprop="name" content="map - cpprefjp C++日本語リファレンス" />
        <meta property="og:title" content="map - cpprefjp C++日本語リファレンス" />
        <meta property="og:url" content="https://cpprefjp.github.io/reference/map/map.html" />
        <meta property="og:site_name" content="cpprefjp - C++日本語リファレンス" />
        <meta property="og:type" content="article" />
        <meta property="og:description" content="`map` はユニークな要素を格納する連想コンテナの一種であり、キーとそれに対応する値を格納する。" />
        <meta name="twitter:card" content="summary" />
        <meta name="twitter:title" content="map - cpprefjp C++日本語リファレンス" />
        <meta name="twitter:url" content="https://cpprefjp.github.io/reference/map/map.html" />
        <meta name="twitter:description" content="`map` はユニークな要素を格納する連想コンテナの一種であり、キーとそれに対応する値を格納する。" />
  <link rel="alternate" type="application/atom+xml" title="Atom" href="https://cpprefjp.github.io/rss.xml" />
<link rel="apple-touch-icon" sizes="180x180" href="../../static/favicons/apple-touch-icon.png?cachebust=be86fa2321ebe02b6955b61b98b778e377bcbf95">
<link rel="icon" type="image/png" sizes="32x32" href="../../static/favicons/favicon-32x32.png?cachebust=be86fa2321ebe02b6955b61b98b778e377bcbf95">
<link rel="icon" type="image/png" sizes="16x16" href="../../static/favicons/favicon-16x16.png?cachebust=be86fa2321ebe02b6955b61b98b778e377bcbf95">
<link rel="manifest" href="../../manifest.json?cachebust=be86fa2321ebe02b6955b61b98b778e377bcbf95">
<meta name="theme-color" content="#f5f8fc">
<link rel="stylesheet" href="../../static/pygments/default.css?cachebust=be86fa2321ebe02b6955b61b98b778e377bcbf95">
<!-- <link rel="stylesheet" href="../../static/css/root.css"> -->
<link href="../../static/kunai/css/kunai-stage-0.css?cachebust=be86fa2321ebe02b6955b61b98b778e377bcbf95" rel="stylesheet">
<link href="../../static/kunai/css/kunai-stage-1.css?cachebust=be86fa2321ebe02b6955b61b98b778e377bcbf95" rel="stylesheet">
<link href="../../static/kunai/css/kunai-stage-2.css?cachebust=be86fa2321ebe02b6955b61b98b778e377bcbf95" rel="stylesheet">
<link href="../../static/kunai/css/kunai-stage-3.css?cachebust=be86fa2321ebe02b6955b61b98b778e377bcbf95" rel="stylesheet">
<script type="text/javascript" src="../../static/kunai/js/kunai-vendor.js?cachebust=be86fa2321ebe02b6955b61b98b778e377bcbf95"></script>
<script type="text/javascript" src="../../static/kunai/js/kunai.js?cachebust=be86fa2321ebe02b6955b61b98b778e377bcbf95"></script>
<script type="text/javascript">
  document.addEventListener('DOMContentLoaded', function() {
    var kn = new Kunai;
    kn.cpprefjp();
    </head>
<header data-kunai-mdinfo="{&#34;meta&#34;: {&#34;header&#34;: [&#34;map&#34;], &#34;namespace&#34;: [&#34;std&#34;], &#34;id-type&#34;: [&#34;class template&#34;]}, &#34;sources&#34;: [{&#34;id&#34;: &#34;b261e3ec0b024175e20e38a9a38d42a7f3919f5a&#34;, &#34;source&#34;: &#34;#include &lt;iostream&gt;\n#include &lt;map&gt;\n\nint main()\n{\n  // char\u3092\u30ad\u30fc\u3001int\u3092\u5024\u3068\u3057\u3066\u6271\u3046\u9023\u60f3\u914d\u5217\n  std::map&lt;char, int&gt; m;\n\n  // \u633f\u5165\n  m.insert(std::make_pair(&#39;c&#39;, 30));\n  m.insert(std::make_pair(&#39;a&#39;, 10));\n  m.insert(std::make_pair(&#39;b&#39;, 20));\n\n  // \u691c\u7d22 : \u30ad\u30fc(char)\u3092\u6307\u5b9a\u3057\u3001\u5024(int)\u3092\u5f97\u308b\n  int value = m.at(&#39;a&#39;);\n  std::cout &lt;&lt; value &lt;&lt; std::endl;\n}\n&#34;}, {&#34;id&#34;: &#34;8d0f01871d471015499b2c8d63ec3ad5d21e02e5&#34;, &#34;source&#34;: &#34;#include &lt;iostream&gt;\n#include &lt;map&gt;\n#include &lt;string&gt;\n#include &lt;tuple&gt;\n\n// \u8981\u7d20\u304c\u3072\u3068\u3064\u306e\u5834\u5408\nstruct MyInt {\n  int value;\n};\n\nbool operator&lt;(const MyInt&amp; a, const MyInt&amp; b) noexcept {\n  return a.value &lt; b.value;\n}\n\n// \u8981\u7d20\u304c\u8907\u6570\u306e\u5834\u5408\nstruct Person {\n  int id;\n  int age;\n  std::string name;\n};\n\nbool operator&lt;(const Person&amp; a, const Person&amp; b) noexcept {\n  // \u30ad\u30fc\u3068\u3057\u3066\u6bd4\u8f03\u3057\u305f\u3044\u8981\u7d20\u3092\u5217\u6319\u3059\u308b\n  return std::tie(a.id, a.age, a.name) &lt; std::tie(b.id, b.age, b.name);\n}\n\nint main() {\n  std::map&lt;MyInt, int&gt; m1 {\n    {MyInt{1}, 3},\n    {MyInt{2}, 1},\n    {MyInt{3}, 4},\n  };\n  std::cout &lt;&lt; m1[MyInt{2}] &lt;&lt; std::endl;\n\n  std::map&lt;Person, int&gt; m2 {\n    {Person{1, 18, \&#34;Alice\&#34;}, 3},\n    {Person{2, 30, \&#34;Bob\&#34;}, 1},\n    {Person{3, 30, \&#34;Carol\&#34;}, 4},\n  };\n  std::cout &lt;&lt; m2[Person{2, 30, \&#34;Bob\&#34;}] &lt;&lt; std::endl;\n}\n&#34;}], &#34;page_id&#34;: [&#34;reference&#34;, &#34;map&#34;, &#34;map&#34;]}">
  <nav class="navbar navbar-default" role="navigation">
    <div class="container-fluid">
      <div class="navbar-header">
        <button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#navbar-collapse">
          <span class="sr-only">Toggle navigation</span>
          <span class="icon-bar"></span>
          <span class="icon-bar"></span>
          <span class="icon-bar"></span>
        </button>
        <a class="navbar-brand" href="../../index.html">
          <div class="title-wrapper clearfix">
            <div class="title">cpprefjp - C++日本語リファレンス</div>
          </div>
        </a>
      </div>
      <div class="collapse navbar-collapse" id="navbar-collapse">
        <ul class="nav navbar-nav navbar-right">
          <li>
            <div class="google-search">
  (function() {
    var cx = '013316413321391058734:ji_u66hl7hq';
    var gcse = document.createElement('script');
    gcse.type = 'text/javascript';
    gcse.async = true;
    gcse.src = (document.location.protocol == 'https:' ? 'https:' : 'http:') +
        '//www.google.com/cse/cse.js?cx=' + cx;
    var s = document.getElementsByTagName('script')[0];
    s.parentNode.insertBefore(gcse, s);
<div class="gcse-search"></div>
            </div>
          </li>
          <li>
  <a href="https://github.com/cpprefjp/site">GitHub Project</a>
        </ul>
      </div>
        <main id="main" role="main">
            <div class="container-fluid">
<div class="row">
  <div class="col-sm-9 col-sm-push-3" itemscope itemtype="http://schema.org/Article">
    <div class="row">
      <div class="col-sm-12 google-search-result">
        <gcse:searchresults></gcse:searchresults>
      </div>
    <div class="row">
      <div class="col-sm-12 content-header">
  <ol class="breadcrumb">
      <li  itemscope itemtype="http://www.schema.org/SiteNavigationElement">
        <span>
            <a href="../../index.html" itemprop="url">
                <i class="fa fa-fw fa-home"></i>
            </a>
        </span>
      </li>
      <li  itemscope itemtype="http://www.schema.org/SiteNavigationElement">
        <span>
            <a href="../../reference.html" itemprop="url">
                <span itemprop="name">リファレンス</span>
            </a>
        </span>
      </li>
      <li  itemscope itemtype="http://www.schema.org/SiteNavigationElement">
        <span>
            <a href="../../reference/map.html" itemprop="url">
                <span itemprop="name">map</span>
            </a>
        </span>
      </li>
      <li class="active" itemscope itemtype="http://www.schema.org/SiteNavigationElement">
        <span>
              <span itemprop="name">map</span>
        </span>
      </li>
  <div class="crsearch"></div>
      </div>
    <div class="row">
      <div class="col-sm-12 edit-button">
    <p class="text-right"><small>
      最終更新日時(UTC):
      <span itemprop="datePublished" content="2025-08-23T16:55:29">
        2025年08月23日 16時55分29秒
      </span>
      <br/>
      <span itemprop="author" itemscope itemtype="http://schema.org/Person">
        <span itemprop="name">Raclamusi</span>
      </span>
    </small></p>
        <p class="text-right">
          <a class="history" target="_blank" href="https://github.com/cpprefjp/site/commits/master/reference/map/map.md">
            <span class="fa fa-fw fa-clock-o fa-flip-horizontal"></span>履歴
          </a>
          <a class="edit" target="_blank" href="https://github.com/cpprefjp/site/edit/master/reference/map/map.md">
            <span class="fa fa-fw fa-pencil"></span>編集
          </a>
        </p>
      </div>
    <div class="row">
      <div class="col-sm-12 content-body">
  <div class="identifier-type">class template</div><div class="header">&lt;map&gt;</div><h1 itemprop="name"><span class="namespace" title="namespace std">std::</span><span class="token">map</span></h1>
<div itemprop="articleBody"><p><div class="codehilite"><pre><span></span><code><span class="k">namespace</span><span class="w"> </span><span class="nn">std</span><span class="w"> </span><span class="p">{</span>
<span class="w">  </span><span class="k">template</span><span class="w"> </span><span class="o">&lt;</span>
<span class="w">        </span><span class="k">class</span><span class="w"> </span><span class="nc">Key</span><span class="p">,</span>
<span class="w">        </span><span class="k">class</span><span class="w"> </span><span class="nc">T</span><span class="p">,</span>
<span class="w">        </span><span class="k">class</span><span class="w"> </span><span class="nc">Compare</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="../functional/less.html">less</a></span><span class="o">&lt;</span><span class="n">Key</span><span class="o">&gt;</span><span class="p">,</span>
<span class="w">        </span><span class="k">class</span><span class="w"> </span><span class="nc">Allocator</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="../memory/allocator.html">allocator</a></span><span class="o">&lt;</span><span class="n"><a href="../utility/pair.html">pair</a></span><span class="o">&lt;</span><span class="k">const</span><span class="w"> </span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="o">&gt;</span>
<span class="w">  </span><span class="o">&gt;</span>
<span class="w">  </span><span class="k">class</span><span class="w"> </span><span class="nc">map</span><span class="p">;</span>
<span class="w">  </span><span class="k">namespace</span><span class="w"> </span><span class="nn">pmr</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="k">template</span><span class="w"> </span><span class="o">&lt;</span><span class="k">class</span><span class="w"> </span><span class="nc">Key</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">T</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">Compare</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="../functional/less.html">less</a></span><span class="o">&lt;</span><span class="n">Key</span><span class="o">&gt;&gt;</span>
<span class="w">      </span><span class="k">using</span><span class="w"> </span><span class="n">map</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="">std::map</a></span><span class="o">&lt;</span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Compare</span><span class="p">,</span>
<span class="w">                           </span><span class="n"><a href="../memory_resource/polymorphic_allocator.html">polymorphic_allocator</a></span><span class="o">&lt;</span><span class="n"><a href="../utility/pair.html">pair</a></span><span class="o">&lt;</span><span class="k">const</span><span class="w"> </span><span class="n">Key</span><span class="p">,</span><span class="w"> </span><span class="n">T</span><span class="o">&gt;&gt;&gt;</span><span class="p">;</span><span class="w">  </span><span class="c1">// C++17から</span>
<span class="w">  </span><span class="p">}</span>
<span class="p">}</span>
</code></pre></div>
<h2>概要</h2>
<p><code>map</code> はユニークな要素を格納する連想コンテナの一種であり、キーとそれに対応する値を格納する。</p>
<p>連想コンテナは特にそれらキーによる要素アクセスが効率的になるよう設計されたコンテナである（要素への相対位置または絶対位置によるアクセスが効率的であるシーケンシャルコンテナとは異なる）。</p>
<p>内部的には、<code>map</code> 内の要素は、コンテナの構築時に設定された<a href="../algorithm.html#strict-weak-ordering">狭義の弱順序</a>基準に従って小さいものから大きいものへとソートされる。 </p>
<p><code>map</code> は一般的に、二分木として実装される。従って、連想コンテナである <code>map</code> の主な特性は以下の通りである。</p>
<li>ユニークな要素のキー：互いに等しい二つのキーを持つ要素が <code>map</code> に格納されることは無い。複数の等しいキーを許す同様の連想コンテナは <code>multimap</code> を参照のこと。</li>
<li>要素の値はキーと値の<code>pair</code>型である。</li>
<li>要素は常に<a href="../algorithm.html#strict-weak-ordering">狭義の弱順序</a>に従う。</li>
<li>挿入操作はイテレータや要素の参照に影響を与えない。</li>
<p>このコンテナクラスは、双方向イテレータをサポートする。</p>
<h2>テンプレートパラメータ</h2>
<li><code>Key</code>: キーの型。キーの値の大小に従って自動的に並び替えられる。</li>
<li><code>T</code>: 値の型。</li>
<li><code>pair&lt;const Key, T&gt;</code>: 要素の型。</li>
<li><code>Compare</code>: 比較クラス。このクラスは 2 つの引数（同じ型）をとり <code>bool</code> 値を返す。<a href="../algorithm.html#strict-weak-ordering">狭義の弱順序</a>において <code>a</code> が <code>b</code> よりも前の場所に位置づけられる場合に <code>true</code> である。これはクラスが関数呼び出しオブジェクトを実装したクラスであっても良いし関数ポインタであっても良い（例は コンストラクタ を参照）。これは、<code>operator&lt;()</code> を適用( <code>a &lt; b</code> )したときと同じ値を返す <code>less&lt;Key&gt;</code> がデフォルトである。</li>
<li><code>Allocator</code>: ストレージアロケーションモデルを決定づける、アロケータオブジェクトの型である。デフォルトでは、<code>pair&lt;const Key, T&gt;</code> への <code><a href="../memory/allocator.html">allocator</a></code> クラステンプレート（これは値に依存しないシンプルなメモリ確保モデルを定義する）が使われる。</li>
<h2>メンバ関数</h2>
<h3>構築・破棄</h3>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
<td><code><a href="map/op_constructor.html">(constructor)</a></code></td>
<td>コンストラクタ</td>
<td><code><a href="map/op_destructor.html">(destructor)</a></code></td>
<td>デストラクタ</td>
<td><code><a href="map/op_assign.html">operator=</a></code></td>
<td>代入演算子</td>
<td><code><a href="map/get_allocator.html">get_allocator</a></code></td>
<td>アロケータオブジェクトを取得する</td>
<h3>イテレータ</h3>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
<td><code><a href="map/begin.html">begin</a></code></td>
<td>先頭を指すイテレータを取得する</td>
<td><code><a href="map/cbegin.html">cbegin</a></code></td>
<td>先頭を指す読み取り専用イテレータを取得する</td>
<td>C++11</td>
<td><code><a href="map/end.html">end</a></code></td>
<td>末尾の次を指すイテレータを取得する</td>
<td><code><a href="map/cend.html">cend</a></code></td>
<td>末尾の次を指す読み取り専用イテレータを取得する</td>
<td>C++11</td>
<td><code><a href="map/rbegin.html">rbegin</a></code></td>
<td>末尾を指す逆イテレータを取得する</td>
<td><code><a href="map/crbegin.html">crbegin</a></code></td>
<td>末尾を指す読み取り専用逆イテレータを取得する</td>
<td>C++11</td>
<td><code><a href="map/rend.html">rend</a></code></td>
<td>先頭の前を指す逆イテレータを取得する</td>
<td><code><a href="map/crend.html">crend</a></code></td>
<td>先頭の前を指す読み取り専用逆イテレータを取得する</td>
<td>C++11</td>
<h3>領域</h3>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
<td><code><a href="map/empty.html">empty</a></code></td>
<td>コンテナが空であるかどうかを調べる</td>
<td><code><a href="map/size.html">size</a></code></td>
<td>要素数を取得する</td>
<td><code><a href="map/max_size.html">max_size</a></code></td>
<td>格納可能な最大の要素数を取得する</td>
<h3>コンテナの変更</h3>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
<td><code><a href="map/clear.html">clear</a></code></td>
<td>全ての要素を削除する</td>
<td><code><a href="map/insert.html">insert</a></code></td>
<td>要素を挿入する</td>
<td><code><a href="map/insert_range.html">insert_range</a></code></td>
<td>Rangeの要素を挿入する</td>
<td>C++23</td>
<td><code><a href="map/insert_or_assign.html">insert_or_assign</a></code></td>
<td>要素を挿入、あるいは代入する</td>
<td>C++17</td>
<td><code><a href="map/emplace.html">emplace</a></code></td>
<td>要素を直接構築する</td>
<td>C++11</td>
<td><code><a href="map/emplace_hint.html">emplace_hint</a></code></td>
<td>ヒントを使って要素を直接構築する</td>
<td>C++11</td>
<td><code><a href="map/try_emplace.html">try_emplace</a></code></td>
<td>キーが存在しない場合のみ要素を直接構築する</td>
<td>C++17</td>
<td><code><a href="map/erase.html">erase</a></code></td>
<td>要素を削除する</td>
<td><code><a href="map/swap.html">swap</a></code></td>
<td>コンテンツを交換する</td>
<td><code><a href="map/extract.html">extract</a></code></td>
<td>ノードハンドルを取得する</td>
<td>C++17</td>
<td><code><a href="map/merge.html">merge</a></code></td>
<td>他のオブジェクトの要素をマージする</td>
<td>C++17</td>
<h3>要素アクセス</h3>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
<td><code><a href="map/op_at.html">operator[]</a></code></td>
<td>指定したキーを持つ要素を取得する</td>
<td><code><a href="map/at.html">at</a></code></td>
<td>指定したキーを持つ要素を取得する</td>
<td>C++11</td>
<td><code><a href="map/count.html">count</a></code></td>
<td>指定したキーにマッチする要素の数を取得する</td>
<td><code><a href="map/find.html">find</a></code></td>
<td>指定したキーで要素を探す</td>
<td><code><a href="map/contains.html">contains</a></code></td>
<td>指定したキーの要素が含まれているかを判定する</td>
<td>C++20</td>
<td><code><a href="map/equal_range.html">equal_range</a></code></td>
<td>指定したキーにマッチする要素範囲を取得する</td>
<td><code><a href="map/lower_bound.html">lower_bound</a></code></td>
<td>与えられた値より小さくない最初の要素へのイテレータを取得する</td>
<td><code><a href="map/upper_bound.html">upper_bound</a></code></td>
<td>特定の値よりも大きい最初の要素へのイテレータを取得する</td>
<h3>オブザーバー</h3>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
<td><code><a href="map/key_comp.html">key_comp</a></code></td>
<td>キー比較用の関数オブジェクトを取得する</td>
<td><code><a href="map/value_comp.html">value_comp</a></code></td>
<td>要素比較用の関数オブジェクトを取得する</td>
<h2>メンバ型</h2>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
<td><code>key_type</code></td>
<td>キーの型。テンプレートパラメータ <code>Key</code>。</td>
<td><code>value_type</code></td>
<td>要素の型。<code>std::<a href="../utility/pair.html">pair</a>&lt;const Key, T&gt;</code>。</td>
<td><code>mapped_type</code></td>
<td>値の型。テンプレートパラメータ <code>T</code>。</td>
<td><code>key_compare</code></td>
<td>キー値の大小関係を判定する二項<a class="cpprefjp-defined-word" data-desc="boolを返す関数・関数オブジェクト。predicate">述語</a>の型。テンプレートパラメータ <code>Compare</code>。</td>
<td><code><a href="map/value_compare.html">value_compare</a></code></td>
<td>要素値のキー部分で大小関係を判定する二項<a class="cpprefjp-defined-word" data-desc="boolを返す関数・関数オブジェクト。predicate">述語</a>の型。入れ子クラス</td>
<td><code>allocator_type</code></td>
<td>アロケータの型。テンプレートパラメータ <code>Allocator</code>。</td>
<td><code>reference</code></td>
<td>要素<code>value_type</code>への参照型。<code>value_type&amp;</code>。</td>
<td><code>const_reference</code></td>
<td>要素<code>value_type</code>への<code>const</code>参照型。<code>const value_type&amp;</code>。</td>
<td><code>iterator</code></td>
<td>双方向イテレータ。</td>
<td><code>const_iterator</code></td>
<td>読み取り専用双方向イテレータ。</td>
<td><code>size_type</code></td>
<td>要素数を表す符号なし整数型。<code>difference_type</code> で表現可能な非負整数（0以上の整数）を表すことが可能。(通常は <code><a href="../cstddef/size_t.html">size_t</a></code>)</td>
<td><code>difference_type</code></td>
<td>同一のコンテナを指す <code>iterator</code> の差を表す符号付き整数型(通常は <code><a href="../cstddef/ptrdiff_t.html">ptrdiff_t</a></code>) <br /><code>std::<a href="../iterator/iterator_traits.html">iterator_traits</a>&lt;iterator&gt;::difference_type</code>、および、<code>std::<a href="../iterator/iterator_traits.html">iterator_traits</a>&lt;const_iterator&gt;::difference_type</code> と同じ。</td>
<td><code>pointer</code></td>
<td>要素 <code>value_type</code>へのポインタ。<br /> C++03 : <code>typename Allocator::pointer</code>。<br /> C++11以降 : <code>typename <a href="../memory/allocator_traits.html">allocator_traits</a>&lt;Allocator&gt;::pointer</code>。</td>
<td><code>const_pointer</code></td>
<td>要素 <code>value_type</code>への<code>const</code>ポインタ。<br /> C++03 : <code>typename Allocator::const_pointer</code>。<br /> C++11以降 : <code>typename <a href="../memory/allocator_traits.html">allocator_traits</a>&lt;Allocator&gt;::const_pointer</code>。</td>
<td><code>reverse_iterator</code></td>
<td>逆順双方向イテレータ。<code>std::<a href="../iterator/reverse_iterator.html">reverse_iterator</a>&lt;iterator&gt;</code>。</td>
<td><code>const_reverse_iterator</code></td>
<td>読み取り専用逆順双方向イテレータ。<code>std::<a href="../iterator/reverse_iterator.html">reverse_iterator</a>&lt;const_iterator&gt;</code>。</td>
<td><code>node_type</code></td>
<td><code><a href="../node_handle/node_handle.html">node_handle</a></code>クラステンプレートの特殊化。</td>
<td>C++17</td>
<td><code>insert_return_type</code></td>
<td>ノードを挿入した結果を記述するために使用されるクラス型。以下に示す<code>insert-return-type</code>テンプレートの特殊化である。ただし、これは説明用のクラスであり、<a class="cpprefjp-defined-word" data-desc="処理系定義の動作。処理系によって事前に定めた動作をする" href="../../implementation-compliance.html#dfn-implementation-defined-behavior">実装定義</a>である。</td>
<td>C++17</td>
<p><div class="codehilite"><pre><span></span><code><span class="k">template</span><span class="w"> </span><span class="o">&lt;</span><span class="k">class</span><span class="w"> </span><span class="nc">Iterator</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">NodeType</span><span class="o">&gt;</span>
<span class="k">struct</span><span class="w"> </span><span class="nc">insert</span><span class="o">-</span><span class="k">return</span><span class="o">-</span><span class="n">type</span><span class="w"> </span><span class="p">{</span>
<span class="w">  </span><span class="n">Iterator</span><span class="w"> </span><span class="n">position</span><span class="p">;</span>
<span class="w">  </span><span class="kt">bool</span><span class="w"> </span><span class="n">inserted</span><span class="p">;</span>
<span class="w">  </span><span class="n">NodeType</span><span class="w"> </span><span class="n">node</span><span class="p">;</span>
<span class="p">};</span>
</code></pre></div>
<h2>非メンバ関数</h2>
<h3>比較演算子</h3>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
<td><code><a href="map/op_equal.html">operator==</a></code></td>
<td>左辺と右辺が等しいかの判定を行う</td>
<td><code><a href="map/op_not_equal.html">operator!=</a></code></td>
<td>左辺と右辺が等しくないかの判定を行う</td>
<td><code><a href="map/op_compare_3way.html">operator&lt;=&gt;</a></code></td>
<td>三方比較を行う</td>
<td>C++20</td>
<td><code><a href="map/op_less.html">operator&lt;</a></code></td>
<td>左辺が右辺より小さいかの判定を行う</td>
<td><code><a href="map/op_less_equal.html">operator&lt;=</a></code></td>
<td>左辺が右辺より小さいか等しいかの判定を行う</td>
<td><code><a href="map/op_greater.html">operator&gt;</a></code></td>
<td>左辺が右辺より大きいかの判定を行う</td>
<td><code><a href="map/op_greater_equal.html">operator&gt;=</a></code></td>
<td>左辺が右辺より大きいか等しいかの判定を行う</td>
<h3>入れ替え</h3>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
<td><code><a href="map/swap_free.html">swap</a></code></td>
<td>2つの<code>map</code>オブジェクトを入れ替える</td>
<h3>要素削除</h3>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
<td><code><a href="map/erase_if_free.html">erase_if</a></code></td>
<td>指定した条件に合致する要素とその分の領域を、コンテナから削除する</td>
<td>C++20</td>
<h2>推論補助</h2>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
<td><code><a href="map/op_deduction_guide.html">(deduction_guide)</a></code></td>
<td>クラステンプレートの推論補助</td>
<td>C++17</td>
<h3>基本的な使い方</h3>
<p><div class="yata" id="b261e3ec0b024175e20e38a9a38d42a7f3919f5a"><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../iostream.html">&lt;iostream&gt;</a></span>
<span class="cp">#include <a href="../map.html">&lt;map&gt;</a></span>
<span class="kt">int</span><span class="w"> </span><span class="nf">main</span><span class="p">()</span>
<span class="p">{</span>
<span class="w">  </span><span class="c1">// charをキー、intを値として扱う連想配列</span>
<span class="w">  </span><span class="n"><span style="color:#ff0000">std::map</span></span><span class="o">&lt;</span><span class="kt">char</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">&gt;</span><span class="w"> </span><span class="n">m</span><span class="p">;</span>
<span class="w">  </span><span class="c1">// 挿入</span>
<span class="w">  </span><span class="n"><a href="map/insert.html">m.insert</a></span><span class="p">(</span><span class="n"><a href="../utility/make_pair.html">std::make_pair</a></span><span class="p">(</span><span class="sc">'c'</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p">));</span>
<span class="w">  </span><span class="n"><a href="map/insert.html">m.insert</a></span><span class="p">(</span><span class="n"><a href="../utility/make_pair.html">std::make_pair</a></span><span class="p">(</span><span class="sc">'a'</span><span class="p">,</span><span class="w"> </span><span class="mi">10</span><span class="p">));</span>
<span class="w">  </span><span class="n"><a href="map/insert.html">m.insert</a></span><span class="p">(</span><span class="n"><a href="../utility/make_pair.html">std::make_pair</a></span><span class="p">(</span><span class="sc">'b'</span><span class="p">,</span><span class="w"> </span><span class="mi">20</span><span class="p">));</span>
<span class="w">  </span><span class="c1">// 検索 : キー(char)を指定し、値(int)を得る</span>
<span class="w">  </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="map/at.html">m.at</a></span><span class="p">(</span><span class="sc">'a'</span><span class="p">);</span>
<span class="w">  </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">value</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="p">}</span>
</code></pre></div>
<h4>出力</h4>
<p><pre><code>10
</code></pre></p>
<h3><a class="cpprefjp-defined-word" data-desc="プログラム定義型。標準ライブラリの型を除く、ユーザー（プログラマ）によって定義された型のこと">ユーザー定義型</a>をキーとして使用する (<code>operator&lt;</code>を定義)</h3>
<p><div class="yata" id="8d0f01871d471015499b2c8d63ec3ad5d21e02e5"><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../iostream.html">&lt;iostream&gt;</a></span>
<span class="cp">#include <a href="../map.html">&lt;map&gt;</a></span>
<span class="cp">#include <a href="../string.html">&lt;string&gt;</a></span>
<span class="cp">#include <a href="../tuple.html">&lt;tuple&gt;</a></span>
<span class="c1">// 要素がひとつの場合</span>
<span class="k">struct</span><span class="w"> </span><span class="nc">MyInt</span><span class="w"> </span><span class="p">{</span>
<span class="w">  </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">;</span>
<span class="p">};</span>
<span class="kt">bool</span><span class="w"> </span><span class="k">operator</span><span class="o">&lt;</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="n">MyInt</span><span class="o">&amp;</span><span class="w"> </span><span class="n">a</span><span class="p">,</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n">MyInt</span><span class="o">&amp;</span><span class="w"> </span><span class="n">b</span><span class="p">)</span><span class="w"> </span><span class="k">noexcept</span><span class="w"> </span><span class="p">{</span>
<span class="w">  </span><span class="k">return</span><span class="w"> </span><span class="n">a</span><span class="p">.</span><span class="n">value</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">b</span><span class="p">.</span><span class="n">value</span><span class="p">;</span>
<span class="p">}</span>
<span class="c1">// 要素が複数の場合</span>
<span class="k">struct</span><span class="w"> </span><span class="nc">Person</span><span class="w"> </span><span class="p">{</span>
<span class="w">  </span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">;</span>
<span class="w">  </span><span class="kt">int</span><span class="w"> </span><span class="n">age</span><span class="p">;</span>
<span class="w">  </span><span class="n"><a href="../string/basic_string.html">std::string</a></span><span class="w"> </span><span class="n">name</span><span class="p">;</span>
<span class="p">};</span>
<span class="kt">bool</span><span class="w"> </span><span class="k">operator</span><span class="o">&lt;</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="n">Person</span><span class="o">&amp;</span><span class="w"> </span><span class="n">a</span><span class="p">,</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n">Person</span><span class="o">&amp;</span><span class="w"> </span><span class="n">b</span><span class="p">)</span><span class="w"> </span><span class="k">noexcept</span><span class="w"> </span><span class="p">{</span>
<span class="w">  </span><span class="c1">// キーとして比較したい要素を列挙する</span>
<span class="w">  </span><span class="k">return</span><span class="w"> </span><span class="n"><a href="../tuple/tie.html">std::tie</a></span><span class="p">(</span><span class="n">a</span><span class="p">.</span><span class="n">id</span><span class="p">,</span><span class="w"> </span><span class="n">a</span><span class="p">.</span><span class="n">age</span><span class="p">,</span><span class="w"> </span><span class="n">a</span><span class="p">.</span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n"><a href="../tuple/tie.html">std::tie</a></span><span class="p">(</span><span class="n">b</span><span class="p">.</span><span class="n">id</span><span class="p">,</span><span class="w"> </span><span class="n">b</span><span class="p">.</span><span class="n">age</span><span class="p">,</span><span class="w"> </span><span class="n">b</span><span class="p">.</span><span class="n">name</span><span class="p">);</span>
<span class="p">}</span>
<span class="kt">int</span><span class="w"> </span><span class="n">main</span><span class="p">()</span><span class="w"> </span><span class="p">{</span>
<span class="w">  </span><span class="n"><a href="">std::map</a></span><span class="o">&lt;</span><span class="n">MyInt</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">&gt;</span><span class="w"> </span><span class="n">m1</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="p">{</span><span class="n">MyInt</span><span class="p">{</span><span class="mi">1</span><span class="p">},</span><span class="w"> </span><span class="mi">3</span><span class="p">},</span>
<span class="w">    </span><span class="p">{</span><span class="n">MyInt</span><span class="p">{</span><span class="mi">2</span><span class="p">},</span><span class="w"> </span><span class="mi">1</span><span class="p">},</span>
<span class="w">    </span><span class="p">{</span><span class="n">MyInt</span><span class="p">{</span><span class="mi">3</span><span class="p">},</span><span class="w"> </span><span class="mi">4</span><span class="p">},</span>
<span class="w">  </span><span class="p">};</span>
<span class="w">  </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">m1</span><span class="p">[</span><span class="n">MyInt</span><span class="p">{</span><span class="mi">2</span><span class="p">}]</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="n"><a href="">std::map</a></span><span class="o">&lt;</span><span class="n">Person</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">&gt;</span><span class="w"> </span><span class="n">m2</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="p">{</span><span class="n">Person</span><span class="p">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">18</span><span class="p">,</span><span class="w"> </span><span class="s">"Alice"</span><span class="p">},</span><span class="w"> </span><span class="mi">3</span><span class="p">},</span>
<span class="w">    </span><span class="p">{</span><span class="n">Person</span><span class="p">{</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p">,</span><span class="w"> </span><span class="s">"Bob"</span><span class="p">},</span><span class="w"> </span><span class="mi">1</span><span class="p">},</span>
<span class="w">    </span><span class="p">{</span><span class="n">Person</span><span class="p">{</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p">,</span><span class="w"> </span><span class="s">"Carol"</span><span class="p">},</span><span class="w"> </span><span class="mi">4</span><span class="p">},</span>
<span class="w">  </span><span class="p">};</span>
<span class="w">  </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">m2</span><span class="p">[</span><span class="n">Person</span><span class="p">{</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p">,</span><span class="w"> </span><span class="s">"Bob"</span><span class="p">}]</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="p">}</span>
</code></pre></div>
<h4>出力</h4>
<p><pre><code>1
</code></pre></p>
<h3><a class="cpprefjp-defined-word" data-desc="プログラム定義型。標準ライブラリの型を除く、ユーザー（プログラマ）によって定義された型のこと">ユーザー定義型</a>をキーとして使用する (大小比較の関数オブジェクトを定義)</h3>
<p><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../iostream.html">&lt;iostream&gt;</a></span>
<span class="cp">#include <a href="../map.html">&lt;map&gt;</a></span>
<span class="cp">#include <a href="../string.html">&lt;string&gt;</a></span>
<span class="cp">#include <a href="../tuple.html">&lt;tuple&gt;</a></span>
<span class="c1">// 要素がひとつの場合</span>
<span class="k">struct</span><span class="w"> </span><span class="nc">MyInt</span><span class="w"> </span><span class="p">{</span>
<span class="w">  </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">;</span>
<span class="p">};</span>
<span class="k">struct</span><span class="w"> </span><span class="nc">MyIntLess</span><span class="w"> </span><span class="p">{</span>
<span class="w">  </span><span class="kt">bool</span><span class="w"> </span><span class="nf">operator</span><span class="p">()(</span><span class="k">const</span><span class="w"> </span><span class="n">MyInt</span><span class="o">&amp;</span><span class="w"> </span><span class="n">a</span><span class="p">,</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n">MyInt</span><span class="o">&amp;</span><span class="w"> </span><span class="n">b</span><span class="p">)</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="k">noexcept</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n">a</span><span class="p">.</span><span class="n">value</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">b</span><span class="p">.</span><span class="n">value</span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="p">};</span>
<span class="c1">// 要素が複数の場合</span>
<span class="k">struct</span><span class="w"> </span><span class="nc">Person</span><span class="w"> </span><span class="p">{</span>
<span class="w">  </span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">;</span>
<span class="w">  </span><span class="kt">int</span><span class="w"> </span><span class="n">age</span><span class="p">;</span>
<span class="w">  </span><span class="n"><a href="../string/basic_string.html">std::string</a></span><span class="w"> </span><span class="n">name</span><span class="p">;</span>
<span class="p">};</span>
<span class="k">struct</span><span class="w"> </span><span class="nc">PersonLess</span><span class="w"> </span><span class="p">{</span>
<span class="w">  </span><span class="kt">bool</span><span class="w"> </span><span class="nf">operator</span><span class="p">()(</span><span class="k">const</span><span class="w"> </span><span class="n">Person</span><span class="o">&amp;</span><span class="w"> </span><span class="n">a</span><span class="p">,</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n">Person</span><span class="o">&amp;</span><span class="w"> </span><span class="n">b</span><span class="p">)</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="k">noexcept</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="c1">// キーとして比較したい要素を列挙する</span>
<span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="n"><a href="../tuple/tie.html">std::tie</a></span><span class="p">(</span><span class="n">a</span><span class="p">.</span><span class="n">id</span><span class="p">,</span><span class="w"> </span><span class="n">a</span><span class="p">.</span><span class="n">age</span><span class="p">,</span><span class="w"> </span><span class="n">a</span><span class="p">.</span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n"><a href="../tuple/tie.html">std::tie</a></span><span class="p">(</span><span class="n">b</span><span class="p">.</span><span class="n">id</span><span class="p">,</span><span class="w"> </span><span class="n">b</span><span class="p">.</span><span class="n">age</span><span class="p">,</span><span class="w"> </span><span class="n">b</span><span class="p">.</span><span class="n">name</span><span class="p">);</span>
<span class="w">  </span><span class="p">}</span>
<span class="p">};</span>
<span class="kt">int</span><span class="w"> </span><span class="nf">main</span><span class="p">()</span><span class="w"> </span><span class="p">{</span>
<span class="w">  </span><span class="n"><a href="">std::map</a></span><span class="o">&lt;</span><span class="n">MyInt</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="p">,</span><span class="w"> </span><span class="n">MyIntLess</span><span class="o">&gt;</span><span class="w"> </span><span class="n">m1</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="p">{</span><span class="n">MyInt</span><span class="p">{</span><span class="mi">1</span><span class="p">},</span><span class="w"> </span><span class="mi">3</span><span class="p">},</span>
<span class="w">    </span><span class="p">{</span><span class="n">MyInt</span><span class="p">{</span><span class="mi">2</span><span class="p">},</span><span class="w"> </span><span class="mi">1</span><span class="p">},</span>
<span class="w">    </span><span class="p">{</span><span class="n">MyInt</span><span class="p">{</span><span class="mi">3</span><span class="p">},</span><span class="w"> </span><span class="mi">4</span><span class="p">},</span>
<span class="w">  </span><span class="p">};</span>
<span class="w">  </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">m1</span><span class="p">[</span><span class="n">MyInt</span><span class="p">{</span><span class="mi">2</span><span class="p">}]</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="n"><a href="">std::map</a></span><span class="o">&lt;</span><span class="n">Person</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="p">,</span><span class="w"> </span><span class="n">PersonLess</span><span class="o">&gt;</span><span class="w"> </span><span class="n">m2</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="p">{</span><span class="n">Person</span><span class="p">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">18</span><span class="p">,</span><span class="w"> </span><span class="s">"Alice"</span><span class="p">},</span><span class="w"> </span><span class="mi">3</span><span class="p">},</span>
<span class="w">    </span><span class="p">{</span><span class="n">Person</span><span class="p">{</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p">,</span><span class="w"> </span><span class="s">"Bob"</span><span class="p">},</span><span class="w"> </span><span class="mi">1</span><span class="p">},</span>
<span class="w">    </span><span class="p">{</span><span class="n">Person</span><span class="p">{</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p">,</span><span class="w"> </span><span class="s">"Carol"</span><span class="p">},</span><span class="w"> </span><span class="mi">4</span><span class="p">},</span>
<span class="w">  </span><span class="p">};</span>
<span class="w">  </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">m2</span><span class="p">[</span><span class="n">Person</span><span class="p">{</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p">,</span><span class="w"> </span><span class="s">"Bob"</span><span class="p">}]</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="p">}</span>
</code></pre></div>
<h4>出力</h4>
<p><pre><code>1
</code></pre></p>
<h3><a class="cpprefjp-defined-word" data-desc="プログラム定義型。標準ライブラリの型を除く、ユーザー（プログラマ）によって定義された型のこと">ユーザー定義型</a>をキーとして使用する (三方比較演算子を定義) (C++20)</h3>
<p><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../iostream.html">&lt;iostream&gt;</a></span>
<span class="cp">#include <a href="../map.html">&lt;map&gt;</a></span>
<span class="cp">#include <a href="../string.html">&lt;string&gt;</a></span>
<span class="c1">// 要素がひとつの場合</span>
<span class="k">struct</span><span class="w"> </span><span class="nc">MyInt</span><span class="w"> </span><span class="p">{</span>
<span class="w">  </span><span class="kt">int</span><span class="w"> </span><span class="n">value</span><span class="p">;</span>
<span class="w">  </span><span class="k">friend</span><span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="k">operator</span><span class="o">&lt;=&gt;</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="n">MyInt</span><span class="o">&amp;</span><span class="p">,</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n">MyInt</span><span class="o">&amp;</span><span class="p">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">default</span><span class="p">;</span>
<span class="p">};</span>
<span class="c1">// 要素が複数の場合</span>
<span class="k">struct</span><span class="w"> </span><span class="nc">Person</span><span class="w"> </span><span class="p">{</span>
<span class="w">  </span><span class="kt">int</span><span class="w"> </span><span class="n">id</span><span class="p">;</span>
<span class="w">  </span><span class="kt">int</span><span class="w"> </span><span class="n">age</span><span class="p">;</span>
<span class="w">  </span><span class="n"><a href="../string/basic_string.html">std::string</a></span><span class="w"> </span><span class="n">name</span><span class="p">;</span>
<span class="w">  </span><span class="k">friend</span><span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="k">operator</span><span class="o">&lt;=&gt;</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="n">Person</span><span class="o">&amp;</span><span class="p">,</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n">Person</span><span class="o">&amp;</span><span class="p">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">default</span><span class="p">;</span>
<span class="p">};</span>
<span class="kt">int</span><span class="w"> </span><span class="nf">main</span><span class="p">()</span><span class="w"> </span><span class="p">{</span>
<span class="w">  </span><span class="n"><a href="">std::map</a></span><span class="o">&lt;</span><span class="n">MyInt</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">&gt;</span><span class="w"> </span><span class="n">m1</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="p">{</span><span class="n">MyInt</span><span class="p">{</span><span class="mi">1</span><span class="p">},</span><span class="w"> </span><span class="mi">3</span><span class="p">},</span>
<span class="w">    </span><span class="p">{</span><span class="n">MyInt</span><span class="p">{</span><span class="mi">2</span><span class="p">},</span><span class="w"> </span><span class="mi">1</span><span class="p">},</span>
<span class="w">    </span><span class="p">{</span><span class="n">MyInt</span><span class="p">{</span><span class="mi">3</span><span class="p">},</span><span class="w"> </span><span class="mi">4</span><span class="p">},</span>
<span class="w">  </span><span class="p">};</span>
<span class="w">  </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">m1</span><span class="p">[</span><span class="n">MyInt</span><span class="p">{</span><span class="mi">2</span><span class="p">}]</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="n"><a href="">std::map</a></span><span class="o">&lt;</span><span class="n">Person</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">&gt;</span><span class="w"> </span><span class="n">m2</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="p">{</span><span class="n">Person</span><span class="p">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">18</span><span class="p">,</span><span class="w"> </span><span class="s">"Alice"</span><span class="p">},</span><span class="w"> </span><span class="mi">3</span><span class="p">},</span>
<span class="w">    </span><span class="p">{</span><span class="n">Person</span><span class="p">{</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p">,</span><span class="w"> </span><span class="s">"Bob"</span><span class="p">},</span><span class="w"> </span><span class="mi">1</span><span class="p">},</span>
<span class="w">    </span><span class="p">{</span><span class="n">Person</span><span class="p">{</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p">,</span><span class="w"> </span><span class="s">"Carol"</span><span class="p">},</span><span class="w"> </span><span class="mi">4</span><span class="p">},</span>
<span class="w">  </span><span class="p">};</span>
<span class="w">  </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">m2</span><span class="p">[</span><span class="n">Person</span><span class="p">{</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p">,</span><span class="w"> </span><span class="s">"Bob"</span><span class="p">}]</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="p">}</span>
</code></pre></div>
<h4>出力</h4>
<p><pre><code>1
</code></pre></p>
<h3>文字列比較のコストを下げる比較関数オブジェクトの指定方法 (C++14)</h3>
<p><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../iostream.html">&lt;iostream&gt;</a></span>
<span class="cp">#include <a href="../map.html">&lt;map&gt;</a></span>
<span class="cp">#include <a href="../string.html">&lt;string&gt;</a></span>
<span class="kt">int</span><span class="w"> </span><span class="nf">main</span><span class="p">()</span><span class="w"> </span><span class="p">{</span>
<span class="w">  </span><span class="c1">// 比較関数オブジェクトをデフォルトの<a href="../functional/less.html">std::less</a>&lt;Key&gt;の代わりに</span>
<span class="w">  </span><span class="c1">// <a href="../functional/less.html">std::less</a>&lt;&gt; (<a href="../functional/less.html">std::less</a>&lt;void&gt;と同じ) と指定する。</span>
<span class="w">  </span><span class="c1">// 検索関係のインタフェースに文字列リテラルを指定した際に</span>
<span class="w">  </span><span class="c1">// キーのための<a href="../string/basic_string.html">std::string</a>オブジェクトが作られない。</span>
<span class="w">  </span><span class="c1">// 余分なメモリ確保を回避できる</span>
<span class="w">  </span><span class="n"><a href="">std::map</a></span><span class="o">&lt;</span><span class="n"><a href="../string/basic_string.html">std::string</a></span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="../functional/less.html">std::less</a></span><span class="o">&lt;&gt;&gt;</span><span class="w"> </span><span class="n">m</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="p">{</span><span class="s">"Alice"</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p">},</span>
<span class="w">    </span><span class="p">{</span><span class="s">"Bob"</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">},</span>
<span class="w">    </span><span class="p">{</span><span class="s">"Carol"</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p">}</span>
<span class="w">  </span><span class="p">};</span>
<span class="w">  </span><span class="c1">// 文字列リテラル"Bob"から<a href="../string/basic_string.html">std::string</a>オブジェクトが作られない</span>
<span class="w">  </span><span class="n">m</span><span class="p">[</span><span class="s">"Bob"</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span>
<span class="w">  </span><span class="c1">// 文字列リテラル"Carol"から<a href="../string/basic_string.html">std::string</a>オブジェクトが作られない</span>
<span class="w">  </span><span class="k">auto</span><span class="w"> </span><span class="n">it</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="map/find.html">m.find</a></span><span class="p">(</span><span class="s">"Carol"</span><span class="p">);</span>
<span class="w">  </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">it</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n"><a href="map/end.html">m.end()</a></span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">it</span><span class="o">-&gt;</span><span class="n">second</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="k">else</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">"not found"</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="p">}</span>
</code></pre></div>
<h4>出力</h4>
<p><pre><code>4
</code></pre></p>
<h2>関連項目</h2>
<li><a href="../../lang/cpp20/consistent_comparison.html">C++20 <code>&lt;=&gt;</code>/<code>==</code>による比較演算子の自動定義</a></li>
<h2>参照</h2>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2669.htm" target="_blank">N2669 Thread-Safety in the Standard Library (Rev 2)</a></li>
</ul></div>
      </div>
    <div id="sidebar" class="col-sm-3 col-sm-pull-9">
            </div>
        </main>
<footer class="footer navbar navbar-default">
  <div class="container-fluid">
    <p><small>
      本サイトの情報は、
        <a href="https://creativecommons.org/licenses/by/4.0/deed.ja" rel="nofollow">クリエイティブ・コモンズ 表示 4.0 非移植 ライセンス(CC BY)</a>
      の下に提供されています。
    </small></p>
    </body>
Provide feedback

Saved searches

Use saved searches to filter your results more quickly

FilesExpand file tree

map.html

Latest commit

History

map.html

File metadata and controls
